tests for variance added; little fixes

idea/testData/checker/Variance.jet

@@ -0,0 +1,40 @@
+package variance
+
+abstract class Consumer<in T> {}
+
+abstract class Producer<out T> {}
+
+abstract class Usual<T> {}
+
+fun foo(c: Consumer<Int>, p: Producer<Int>, u: Usual<Int>) {
+    val c1: Consumer<Any> = <error>c</error>
+    val c2: Consumer<Int> = c1
+
+    val p1: Producer<Any> = p
+    val p2: Producer<Int> = <error>p1</error>
+
+    val u1: Usual<Any> = <error>u</error>
+    val u2: Usual<Int> = <error>u1</error>
+}
+
+//Arrays copy example
+class Array<T>(val length : Int) {
+    fun get(index : Int) : T { return null }
+    fun set(index : Int, value : T) { /* ... */ }
+}
+
+fun copy1(from : Array<Any>, to : Array<Any>) {}
+
+fun copy2(from : Array<out Any>, to : Array<in Any>) {}
+
+fun <T> copy3(from : Array<out T>, to : Array<in T>) {}
+
+fun copy4(from : Array<out Number>, to : Array<in Int>) {}
+
+fun f(ints: Array<Int>, any: Array<Any>, numbers: Array<Number>) {
+    copy1<error>(ints, any)</error>
+    copy2(ints, any) //ok
+    copy2<error>(ints, numbers)</error>
+    copy3<Int>(ints, numbers)
+    copy4(ints, numbers) //ok
+}